Pressure control device



April 10, 1962 W. L- CARLSON, JR

PRESSURE CONTROL DEVICE Filed Dec. 10, 1956 2| 22 23 36% LOAD POWER 234 M ll 40 46 Q 43 f i::

2 POWER a 47 CONTROL INVEN TOR. WILLIAM L. CARLSON JR BY Z ATTORAEY UflilE Statgs Patefit I 1 a r 3,029,323 PRESSURE CONTROL DEVICE Will am L. Carlson, Jr., Bloomington, Minrn, assignor to M nneapol s-Honeywell Regulator Company, Minneapolls, M nn a corporation of Delaware Filed Dec-.19, 1956,Ser. No. 627,321 9 Claims. (Cl. ZOE-8L6) 'lhis invention relates to a conductive fluid or liquid metal relay and more particularly is directed to a relay used w1th an integral secondary fluid sensing element to form a pressure control device.

The principle of the -col'lduc-tive fluid relay has been known for a number of years. in its simplest form it consists of a pump moving a conductive fluid in or out of a chamber to control an electric circuit by opening or closing an electrical path between two electrodes. This type of relay has been of little practical use because of nherent, complex mechanical problems and time delays in operation. Certain of these disadvantages can be llil'llZEd with the novel features herein disclosed, to obtain a new and very useful type of pressure control device. These features will be explained in some detail after an explanation of the device has been presented. v It is the object of this invention to disclose a conductive fluid relay and pressure control device which provides novel high and/or low pressure cutout features.

It is a further object of this invention to disclose a pressure control device which controls electric circuits as a function of both its own energization and the amount of pressure applied to the system in which it is connected.

Still a further object of this invention is to disclose a pressure control device having far fewer moving parts than normally found in devices which attempt to accomplish the same general type of function.

Another object is to provide a pressure responsive device which is easily adjusted or set electrically from a remote location.

These and other objects will become apparent when the following description is considered With the single sheet of attached drawings, wherein:

FIGURE 1 is a schematic representation of the novel device disclosed in one'of its many embodimntsand;

FIGURE 2 is a cross section along the lines 2-2 of a pump shown in FIGURE 1.

In FIGURE 1, two reservoirs 10 and 11 are disclosed interconnected by a tube 12. The tube, 12 is preferably of an insulating materialv but may be of any convenient materialif proper precautions are taken in constructing the pump generally shown at 14. The pump 14 can be placed at any location intermediate the reservoirs 10' and 11, but for convenience sake it has been disclosed as being approximately intermediate of these two reservoirs. The details of the construction of pump 14, which is known as a Faraday pump, will be more fully set out below, but for the present it is sufficient to understand that pump 14 is capable of moving a conductive fluid 13 which partially fills the reservoirs 10 and 11 and completely fills the tube 12. g Inserted in the top of reservoir 10 are two electrodes 15 and 16. Electr'ode'sls and 16 are insulated at 17 and are connected in a series circuit formed of conductor 20, a load to be controlled 21, conductors 22, a power source 23, and a conductor 24. It will be understood that if the conductive fluid 13' rises sufiicicufly in r se r that electrodes 15 and 16 will be shorted together by thefluid and the circuit through the load 21 and power source 23 wil l thereby be completed. A small tube 30 is 'insiertedjatthe top of reservoir and connects the reservoir 10 to a bellows 31. v The bellows s1 is com pletely sealed am therefore the reservoir 10' and the,

Patented Apr. 10, 1952 bellows 31 form a completely sealed chamber which has a variable volume. It the bellows 31 is distorted for any particular reason, it is apparent that the total volume of the reservoir 19, which would include the bellows 31 and a tube 30, would be varied. Above fluid 13 and filling bellows 31 is any type of atmosphere compatible with fluid 13 so that pressures may be transmitted.

The bellows 31 is enclosed in a pressure tight container 32 which is in turn connected to a pipe 33. By apply- 'ing a pressure or vacuum to the pipe 33 it would be possible to compress or expand bellows 31 and thereby effect the total volume contained in the bellows 31, tube 30 and reservoir 10. 7

Associated with reservoir 11 there is a tube 34, which issimilar to tube 30 in that it connects to a bellows 35, which in turn is enclosed in a pressure tight container 36 having a tube 37. It again is apparent that any pressure or vacuum applied through tube 37 will cause the bellows to collapse or eitpand, thereby changing the total volume of the bellows 35, tube 34 and reservoir 11 by acting upon an atmosphere above fluid 13. It is further apparent that fixed reservoirs 10 and 11 and bellows 31 and 35 could be replaced by reservoir bellows alone.

In considering the system disclosed to this point, it becomes obvious that if the pump 14 is disregarded that pressures or vacuums applied to tubes 33 and 37 will normally cause a shift in the level of fluid 13 in reservoirs 1'0 and 11. If the shift in level of the conductive fluid 13 is adequate it is possible to short circuit the electrodes 15 and 16 and thereby obtain control of the load 21. It is further understood that the tube 34 could be completely sealed off and the bellows 3S, pressure container 36, and tube 37 not used. In this particular case, any

. pressure or vacuum applied to tube 33 would in itself cause a shift of the conductive fluid 13 in the reservoirs 10 and 11 such as to assume control of the load 21.

The function and construction of pump 14 will now be disclosed so that the over-all operation of the pressure control device will become apparent. The pump 14 can be of any convenient type but is preferably of the type known as the Faraday type. The Faraday pump 14 moves the conductive fluid 13 in pipe 12 by the interaction of mutually perpendicular electric currents and magnetic fields. In FIGURE 2 there is disclosed a cross section of a simple form of the Faraday pump. This ptunp includes a C-shaped magnetic structure 40 having a coil 41 encircling any part of the magnetic structure '40. Upon the energization of the coil 41 a magnetic field is established across the tube 12 which passes through the open part or gap in the magnetic structure 40. Inserted into the sides of the tube 12 are two electrodes 42 and 43. These two electrodes are placed in a line with one another and this line is perpendicular to the line or the flux across tube "12. If current is passed between electrodes 42 and 43 while a magnetic flux exists across tube 12, a force is created in the conductive fluid 13 and the fluid is caused tobe moved or pumped. It will be understood that the direction of flow of the fluid or the pressure in the fluid isa function of the direction of the flow of current with respect to the flux of an existing magnetic field. If either the direction of current or the direction of the flux is altered the direction of the force in the fluid is reversed and thereby a completely reversible pump is obtained which has no moving parts and which has a continual open channel identical in size with the pipe 12. It will become obvious therefore that the presently disclosed pump creates no interference with the movement of the conductive fluid 13 when it is de-eneo gized but does influence the movement of the conductive fluid 13 when power is suppliedto the pump 14.

In order to supply the necessary power for the pump 14 a power and control unit 44 is provided. The power and control unit 44 has two leads 45 and 46 which are connected to coil 41 and thus supply coil 41 with the necessary electrical energy to establish a magnetic flux in the core 40. The power and control unit 44; further has conductors 47 and 48 which are connected directly'to the electrodes 42 and 43. The conductors 4'7 and 48 supply the necessary electrical current to the electrodes so that the current necessary for the operation of the pump is available. The nature of the power and control unit 44 is well known to those versed in the art and will not be explained in further detail.

By superimposing the pumping pressure of pump 14 (which is reversible) with that created under the influence of pressure and/or vacuums supplied to pipes 33 and 37 it can be seen that a pressure control device having unusual characteristics is provided. The operation of load 21 can be accomplished either by the direct application of pressure or vacuum from tubes 33 or 37, or by the pumping pressure developed by pump 14. It is also possible to control load 21 by any combination of pressure and vacuum through pipes 33 and 37 and a pumping pressure from pump 14. It becomes obvious therefore that many possible applications for this type of pressure control device could be established.

A specific example of an application and operation of this novel pressure control device is as a low pressure cut-in with an air supply system. As such a low pressure cut-in, the pipe 33 would be connected to any point in an air supply system (not shown) that had a pressure present. The pipe 37 would be vented to the atomsphere, while the load 21 would represent the compressor in the system. When the power and control unit 44 was energizing the pump 14 with a fixed voltage on conductors 45 and 46 and a fixed current on conductors 47 and 48, the pump 14 would supply a constant pressure on the fluid 13 tending to move the fluid into reservoir 10. The movement of the fluid would be restrained by the pressure in the rservoir and bellows 31. If the pressure in the air supply system (not shown) dropped the bellows 31 would expand and the fluid 13 would rise in reservoir 10. When the fluid 13 rose enough in rservoir 10 because of the low pressure in chamber 32, the electrodes 15 and 16 would be shorted by the conductive fluid and the compressor (load 21) would operate to return the pressure in chamber 32 to the desired level.

If it became desirable to change the pressure setting or control point, this can be accomplished from the remote location of the power and control unit by changing either the voltage on conductors and 46 or by changing the current supplied on conductors 47 and 48. Also, a new pressure could be set from this remote location by changing both the energizing current and voltage. This arrangement provides a simple electrical remote setting and overcomes the complex mechanical arrangement currently used in general remote control mechanical systems of this type. In general, remote mechanical systems are diflicult to use due to their complexity and the present would inexpensively solve this long existing problem in the remote control field.

With the arrangement disclosed an endless number of possible combinations of pressures could be set into the overall system shown in FIGURE 1 and it becomes obvious that this system could therefore be applied in numerous Ways. With this in mind the applicant wishes to be limited only to the scope of the appended claims.

I claim as my invention:

1. 'A control device of the class described: power means; a pump energized by said power means and having an inlet and an outlet; said pump'developing a pressure upon the energization of said pump by said power means; reservoir means connected to said inlet and outlet; said reservoir means being partially filled with an electrically conductive fluid and further having a variable volume; current control means operatively inserted in said reservoir means and including external circuit means; and external force means acting on said reservoir means to change its volume in conjunction with said pumping pressure to vary the level of said fluid in said reservoir means; said external circuit means controlled by said conductive fluid acting on said current control means when said level changes.

2. A control device of the class described: power means; a conductive fluid pump energized by said power means and having an inlet and an outlet; said pump developing a pressure upon the energization of said pump by said power means; reservoir means connected to said inlet and outlet; said reservoir means being partially filled with an electrically conductive fluid and further having a variable volume; current control means operatively inserted in said reservoir means and including external circuit means; and external pressure means acting on said reservoir means to change its volume in conjunction with said pumping pressure to vary the level of said fluid in said reservoir means; said external circuit means controlled by said conductive fiuid acting on said current control means when said level changes.

3. A control device of the class described: power means; a conductive fluid pump energized by said power means, and having an inlet and an outlet; said pump developing a pressure upon the energization of said pump by said power means; reservoir means connected to said inlet and outlet; said reservoir means being partially filled with an electrically conductive fluid and further having a variable volume; electrode means operatively inserted in said reservoir means and including external circuit means; and external force means acting on said reservoir means to change its volume in conjunction with said pumping pressure to vary the level of said fluid in said reservoir means; said external circuit means controlled by said conductive fluid acting on said electrode means when said level changes.

4. A control device of the class described: power means; a conductive fluid pump energized by said power means and having an inlet and an outlet; said pump developing a pressure which is a function of the energizetion of said pump; reservoir means connected to said inlet and outlet; said reservoir means being partially filled with an electrically conductive fluid and further having a variable volume; electrode means operatively inserted in said reservoir means and including external circuit means; and external force means acting on said reservoir means to change its volume in conjunction with said pumping pressure to vary the level of said fluid in said reservoir means; said external circuit means controlled by said conductive fluid acting on said electrode means when said level changes.

5. A control device of the class described: power means; an electromagnetic pump energized by said power means and having an inlet and an outlet; said pump developing a pressure which is a function of the energization of said pump; reservoir means connected to said inlet and outlet; said reservoir means being partially filled with a liquid metal and further having a variable volume; electrode means operatively inserted in said reservoir means and including external circuit means; and external force means acting on said reservoirmeans to change its volume in conjunction with said pumping pressure to vary the level of said liquid metal in said reservoir means; said external circuit means controlled by said liquid metal acting on said electrode means when said level changes.

6. A control device of the class described: power means; an electromagnetic liquid metal pump energized by said power means and having an inlet and an outlet; said pump developing a pressure which is substantially proportional to the energization of said pump; reservoir means including a bellows connected to said inlet and outlet; said reservoir means being partially filled with a liquid metal and further having a variable volume; electrode means operatively inserted in said reservoir means and including external circuit means; and pressure means acting on said bellows to change its volume in conjunction with said pumping pressure to vary the level of said liquid metal in said reservoir means; said external circuit means controlled by said liquid metal shorting said electrode means when said level changes.

7. In a control device of the class described: two reservoirs joined by a passage and including a conductive fluid therein; a conductive fluid pump included in said passage; said pump being capable of moving said conductive fluid under pressure from the said first reservoir to the said second reservoir; pressure differential means connected to said reservoirs to vary the pressure upon the conductive fluid independently of said pump pressure; and current control means in one said reservoir; said conductive fluid level being varied by the joint pressures of said pump and said differential means to operate said current control means.

8. In a current control device of the class described: two reservoirs joined by a passage and including a liquid metal therein; a liquid metal pump included in said passage; said pump being capable of moving said liquid metal under pressure from the said first reservoir to the said second reservoir; pressure differential means connected to said reservoirs to vary the pressure upon the liquid metal independently of said pump pressure; and

current control means in one said reservoir; said liquid metal level being varied by the joint pressures of said pump and said differential means to operate said current control means.

9. In a control device of the class described; two reservoirs joined by a pipe and including a liquid metal therein; an electromagnetic liquid metal pump included in said pipe; said pump being capable of moving said liquid metal under pressure from the said first reservoir to the said second reservoir; pressure difierential means connected to said reservoir to vary the pressure upon the liquid metal independently of said pump pressure; and electrodes in one said reservoir; said liquid metal level being varied by the joint pressures of said pump and said difier-ential means to short circuit said electrodes.

References Cited in the file of this patent UNITED STATES PATENTS 1,747,044 Bainbridge Feb. 11, 1930 1,773,036 FitzGe-rald Aug. 12, 1930 1,916,427 Korver July 4, 1933 1,977,498 Staegemann Oct. 16, 1934 2,635,637 Karrer Apr. 21, 1953 FOREIGN PATENTS 900,385 France Oct. 2, 1944 

